Fixed SecurityException for some Android versions.

At the same time removed necessity to register a cryptography provider which means SpongyCryptography can be used on the Oracle JVM as well - but this is something vor Jabit 3.0.

cryptography-sc/build.gradle

@@ -14,4 +14,5 @@ dependencies {
     compile project(':core')
     compile 'com.madgag.spongycastle:prov:1.52.0.0'
     testCompile 'junit:junit:4.12'
+    testCompile 'org.mockito:mockito-core:1.10.19'
 }